Thermoregulation and metabolism
Résumé
Studies in adult humans and animals have demonstrated that sleep and body thermoregulation are closely linked. In a cool or warm environment, there is a functional conflict between the need for sleep and the maintenance of body homeothermia. This conflict might be especially harmful in infants.
This chapter reviews sleep-thermoregulation interactions in neonates and infants, together with the implications of these interactions: thermoregulatory responses can differ according to the sleep stage, and sleep can be deteriorated or improved by a non-thermoneutral environment or by slight manipulations of body temperatures.
In contrast to adults, the neonate’s thermoregulatory system is fully operational during rapid eye movement (REM) sleep, which protects him/her from long periods of poikilothermy. The lack of data on this aspect in older infants or adolescents means that we do not currently know when the switch from neonatal characteristics (greater thermoregulatory efficiency and a greater amount of REM sleep when exposed to a cool environment) to adult characteristics (i.e., poor thermoregulatory efficiency and partial REM sleep deprivation in cool or warm conditions) occurs.
In adults, sleep is regulated in parallel with the circadian rhythm in body temperatures. Similarly, distal skin vasodilation before sleep can be observed as a part of “sleep preparedness” in infants (from preterm neonates to older children). This vasodilation is observed despite age-related differences in sleep structure, rhythm and maturation, and thermoregulatory functions and centers.
These observations raise the question of whether thermal or nonthermal manipulation could improve infants’ sleep by inducing distal cutaneous vasodilation.